Stable dispersions of polyureas and polyhydrazodicarbonamides in polyols ("PHD-polyols") have achieved great commercial importance as starting materials for the production of polyurethane materials including flexible foams, integral skin foams for bumpers, shoe soles, moped saddles, adhesives, coatings, joint casting compounds and the like. Foam seats from PHD-polyols are produced for the automobile industry, particularly in the United States.
Various processes have become known over the last 20 years for the production of such dispersions by reacting organic isocyanates with primary and/or secondary amino group-containing polyamines and/or hydrazines and/or hydrazides in relatively high molecular weight polyols.
Such dispersions can, for example, be produced according to German Auslegeschrift No. 1,260,142 (U.S. Pat. No. 3,325,421), by dissolving the amine component in the polyether. The diisocyanate is then added dropwise at room temperature. Even small quantities of the polyaddition product (2-5%) produce a substantial rise in viscosity. Polyethers having substantial amounts of primary hydroxyl groups (which are of particular importance for modern applications) are not mentioned.
Low-viscous, stable dispersions of polyureas and/or polyhydrazodicarbonamides are produced in situ according to German Pat. Nos. 2,513,815, 2,550,833 and 2,550,862 (U.S. Pat. No. 4,089,835) by continuously reacting organic polyisocyanates with primary and/or secondary amino group-containing polyamines and/or hydrazines and/or hydrazides in relatively high molecular weight polyols in a continuous flow mixer and by subsequently collecting the product leaving the pipeline mixer in a receiver. Water, which is optionally present, may be simultaneously or subsequently removed under vacuum. Polyurea dispersions can also be produced discontinuously by further processes described in German Offenlegungsschrift No. 2,550,796 (U.S. Pat. No. 4,093,569) or German Offenlegungsschrift No. 2,550,797 (U.S. Pat. No. 4,147,680). Low viscosities are achieved by the proportionate use of water as a reaction medium.
Only those products which are produced according to the teaching of German Pat. No. 2,513,815 (U.S. Pat. No. 4,089,835) have generally achieved commercial success.
In comparison with the pure polyethers (and other polyols), the polyurea dispersions produce polyurethane plastics with many advantages. Thus, for example, foaming-reliability is improved in the case of flexible foam blocks and in cold mold foaming. Furthermore, a more advantageous hardness/apparent density relation for the foams is achieved. In the case of integral skin foams, the modulus and rigidity are improved. The adhesion is improved in the case of adhesives. Even stricter demands are made on foams with respect to very good hardness (e.g., load bearing properties). Consequently it was necessary to further develop dispersions containing high quantities of filler and simultaneously low viscosities. The products of prior art do not meet or inadequately meet these demands, particularly if polyphenyl-polymethylene-polyisocyanates ("crude MDI") are used as the isocyanate component to produce the dispersions.